Needle biopsies are common procedures for the diagnosis and staging of disease. These procedures are often done under ultrasound guidance to allow physicians performing the procedure to visualize the position of the needle in relation to target and surrounding tissue structures. Thus, the echogenicity of the needle (i.e., the visibility of the needle under ultrasound) often impacts the success of the procedure. The echogenecity may be affected by the size of the needle, a difference between the acoustic impedance of the needle and that of the surrounding tissue, an angle of the needle relative to the transducer, the frequency of the ultrasound energy used and various characteristics of the processing algorithm.
Various techniques have been developed in an attempt to improve the echogenic properties of needles including mechanical treatments of the outer surface of the needle or echogenic coatings. However, the current mechanical treatments involving the creation of discrete shapes repeated along the axis and/or about the circumference of a needle are complex to form. Other mechanical treatments include the formation of circumferential grooves or spirals around the needle. However, these grooves are tuned to only one angle and one frequency such that a slightly different spacing and/or a different frequency may have a significant negative impact on echogenic performance. The application of echogenic coatings increases the complexity of the devices and does not necessarily enhance the performance of these coated devices relative to the mechanical treatments described above. Furthermore, the echogenic properties of these coatings may decay over time.